News Features

In 2000, Haywood County, NC experienced
its 4th highest 8-hour ozone concentration at 0.085 ppm. On May
1, a daily maximum 8-hour average concentration of 0.089 ppm
was experienced. A detailed meteorological analysis suggests
that stratospheric ozone played an important role in this ozone
episode. Please visit our web site
for more information.

Low-resolution chemical transport models
are underestimating actual background ozone concentrations at
both low - and high-elevation monitoring sites. EPA's Clean Air
Scientific Advisory Committee is concerned about the uncertainty
associated with the models to estimate background levels. Learn
more about background ozone by clicking here.

Can we attain the 8-hour ozone standard?
Find out by learning more about the "Piston Effect"
by clicking here.

Over
the past several years, A.S.L. & Associates and its consultants
have commented on the strengths and weaknesses associated with
the mathematical and statistical methodologies used in epidemiological
studies to link exposure with human health effects. On May 30,
2002, the EPA was informed by the Health Effects Institute (HEI)
of a generally unappreciated aspect in the use of S-Plus statistical
software often employed to fit generalized additive models (GAM)
to data in time-series analyses. Additional background information
is available by clicking here.

Beginning in September 1994, under a grant
from the U.S. Department of Energy, A.S.L. & Associates and
its subcontractor, CAPITA at Washington University St. Louis,
and consultant Dr. Peter Brimblecombe combined talents to develop
a database that allows for the estimation of the global emissions
of sulfur from 1850 to 1990. A common methodology was applied
across all years and countries for the estimation of sulfur emissions.
Please visit our web page for more information.

Concerns about attaining the 8-hour ozone standard because
of the "piston" effect appear to be realistic based
upon EPA's latest trends report.

EPA has summarized ozone trends for the
periods 1980-2016, 1990-2016, 2000-2016, and 2010-2016. EPA notes
that levels are still decreasing nationwide, but the rate of
decrease for 8-hour levels has slowed. Please visit www.epa.gov/airtrends/ozone.html for more information.

Biological evidence developed under both
experimental and actual ambient conditions indicate that, in
general, the higher hourly average concentrations are potentially
more important than the mid- and low-level hourly average concentrations
in eliciting an adverse effect on vegetation. We are continuing
our collaboration with researchers from around the world in developing
flux-based ozone models, which include the quantification of
defense mechanisms, to describe the relationship between exposure,
dose, vegetation effects, and the standard-setting process. Please
visit our web page for more information.

In March 2008, the EPA Administrator lowered
the 8-hour human health and vegetation ozone standards to 0.075
ppm. On September 16, 2009, the EPA announced that it was reviewing
the March 2008 decision. On October 1, 2015, the EPA set new
8-hour standards at 0.070 ppm. Please click
here for additional information.

TheW126 Exposure
Index

The EPA is using the W126 cumulative exposure
index as an indicator to use to protect vegetation. Dr. Lefohn,
President of A.S.L. & Associates, developed and proposed
this index in 1985 as a way to protect vegetation from ozone
exposures. Learn more about the W126 exposure
index.